Multi-phase, single point, short gun perforation device for oilfield applications

ABSTRACT

An apparatus for perforating an unconventional subterranean formation includes a charge holder having a passage along a long axis, a detonating device positioned in the passage and a plurality of shaped charges supported by the charge holder and circumferentially distributed along a same plane that is transverse to the long axis. Each shaped charge is formed of at least a charge case, an explosive material disposed in the charge case, and a liner enclosing the explosive material in the charge case. All of the shaped charges are directly energetically coupled to the detonating device.

BACKGROUND OF THE DISCLOSURE 1. Field of Disclosure

The present disclosure relates to an apparatus and method for completinga well.

2. Description of the Related Art

Hydrocarbons, such as oil and gas, are produced from cased wellboresintersecting one or more hydrocarbon reservoirs in a formation. Thesehydrocarbons flow into the wellbore through perforations in the casedwellbore. Perforations are usually made using a perforating gun loadedwith shaped charges. The gun is lowered into the wellbore on electricwireline, slickline, tubing, coiled tubing, or other conveyance deviceuntil it is adjacent to the hydrocarbon producing formation. Thereafter,a surface signal actuates a firing head associated with the perforatinggun, which then detonates the shaped charges. Projectiles or jets formedby the explosion of the shaped charges penetrate the casing to therebyallow formation fluids to flow through the perforations and into aproduction string.

Conventional perforating tool generate a shot pattern placing tunnelsprincipally along an axial length of a wellbore. The present disclosureproposes non-conventional perforating tools that may enhance completionactivity such as hydraulic fracturing.

SUMMARY OF THE DISCLOSURE

In aspects, the present disclosure provides an apparatus for perforatinga subterranean formation. The apparatus may include a charge holderhaving a passage along a long axis; a detonating device positioned inthe passage; and a plurality of shaped charges supported by the chargeholder and circumferentially distributed along a same plane that istransverse to the long axis. Each shaped charge is formed of at least acharge case, an explosive material disposed in the charge case, and aliner enclosing the explosive material in the charge case. All of theshaped charges are directly energetically coupled to the detonatingdevice.

In further aspects, the present disclosure provides a method forperforating an unconventional subterranean formation. The method mayinclude positioning the above-described apparatus in a wellbore andfiring the apparatus.

The above-recited examples of features of the disclosure have beensummarized rather broadly in order that the detailed description thereofthat follows may be better understood, and in order that thecontributions to the art may be appreciated. There are, of course,additional features of the disclosure that will be described hereinafterand which will form the subject of the claims appended hereto.

BRIEF DESCRIPTION OF THE DRAWINGS

For detailed understanding of the present disclosure, references shouldbe made to the following detailed description of the preferredembodiment, taken in conjunction with the accompanying drawings, inwhich like elements have been given like numerals and wherein:

FIG. 1 is a schematic sectional view of a portion of a horizontal wellin which are positioned perforating guns according to embodiments of thepresent disclosure;

FIGS. 2A and 2B illustrate shot patterns obtained by perforating gunsshown in FIG. 1;

FIG. 3A is an isometric view of a charge holder made in accordance withone embodiment of the present disclosure;

FIG. 3B is an isometric view of an charge holder made in accordance withone embodiment of the present disclosure;

FIG. 4 is a schematic sectional view of a carrier in accordance with oneembodiment of the present disclosure;

FIG. 5 is a schematic sectional view of one embodiment of an apparatusof the present disclosure as positioned within a well penetrating asubterranean formation;

FIG. 6 is a schematic side view of a perforating gun in accordance withone embodiment of the present disclosure that uses one or more scallops;

FIGS. 7A-C illustrate various detonation arrangements for perforatingguns made in accordance with embodiments of the present disclosure;

FIGS. 8A, B illustrate segmented cases for perforating guns made inaccordance with embodiments of the present disclosure;

FIG. 9 is an exemplary shaped charge that may be used with perforatingguns in accordance with embodiments of the present disclosure;

FIG. 10 is schematically illustrates a single detonating device being inenergetic contact with a plurality of shaped charges on a single planein accordance with embodiments of the present disclosure; and

FIG. 11 is schematically illustrates a pocket for receiving a shapedcharge in accordance with embodiments of the present disclosure.

DETAILED DESCRIPTION OF THE DISCLOSURE

Aspects of the present disclosure provide methods and relatedperforating tools for completing unconventional formations, such ashydrocarbon-bearing shale formations. For the present disclosure, an“unconventional” formation is generally a formation that has apermeability that is less than ten millidarcy (mD). Many“unconventional” formations have a permeability between one nano-darcy(nD) and one millidarcy (mD).

Referring to FIG. 1, there is shown a horizontal section of a wellbore10 in which are positioned perforating guns 50, 60 in accordance withembodiments of the present disclosure. Each gun 50, 60 includes shapedcharges 70. The gun 50 has the shaped charges distributedcircumferentially on one plane 72. The gun 60 has the shaped chargesdistributed circumferentially on two planes 74, 76. The planes 72, 74,76 of FIG. 1 are transverse to a long axis 11 of the wellbore 10, e.g.,the axis along which fluid flows along the wellbore 10.

The number of shaped charges 70 on each plane may be varied to suit aparticular situation. A plane may include only one shaped charge 70 orfour or more shaped charges 70. In certain situations, two or threeshaped charges 70 may be used. While not required, shaped charges 70 aretypically evenly distributed along their respective planes; e.g., 180degrees apart for two shaped charges 70, 120 degrees apart for threeshaped charges 70, 90 degrees apart for four shaped charges 70, etc. Themaximum number of shaped charges 70 on a particular plane depends, inpart, on the dimensions of the shaped charge, the charge holdingstructure, and the carrier tube.

FIG. 2A illustrates the “shot pattern” 52 that can be obtained by thegun 50 (FIG. 1), assuming four shaped charges 70 are used. In oneembodiment, the perforating gun 50 is configured to form a shot pattern52 that has perforations 80 of limited penetration. For example, theperforations 80 extend through a casing 12 and cement sheath 14, butextend only minimally, if at all, into a surrounding formation 16.

FIG. 2B illustrates the “shot pattern” 62 that can be obtained by thegun 60 (FIG. 1), assuming four shaped charges 70 are used at each plane74, 76. The shot pattern 62 includes a first set 64 of visibleperforations and a second set 66 of hidden perforations 80. It should benoted that the shaped charges 70 of each plane 74, 76 are out of phaseby forty-five degrees with one another.

FIG. 3A illustrates one non-limiting embodiment of a charge holder 90for the gun 50 (FIG. 1). The charge holder 90 may be a cylindrical bodythat includes cavities 92 in which the shaped charges 70 (FIG. 1) areseated. In one arrangement, the cavities 92 may be pockets formed andcircumferentially distributed on an outer surface 91 of the body 93.Each cavity 92 may be defined by an interior seating surface 95 againstwhich the shaped charge 70 (FIG. 1) seats. Certain embodiments may use acup or conical shape for the seating surface 95. That is, the seatingsurface 95 may generally follow the curvature or angle of a body of ashaped charge 70 (FIG. 1); i.e., the seating surface 95 is complementaryto the body of the shaped charge 70 (FIG. 1). In some embodiments, theseating surface 95 may restrict radially inward and/or lateral movementof the shaped charge 70 (FIG. 1). The charge holder 90 may be formed ofsteel or be molded of a non-metal material such as plastic. The shapedcharges 70 (FIG. 1) may be press fit into the cavities 92 or secured inthe cavities 92 using fastening elements (not shown) such as clips,tabs, etc.

For arrangements using four shaped charges 70 (FIG. 1), the chargeholder 90 may include four circumferentially distributed cavities 92,which are all arranged along the same plane 72 (FIG. 1). One or morepassages 94 may be used to route equipment such as a detonating device(not shown) and/or wiring (not shown). The passage 94 may be an internalbore that extends partially or completely through the body 93. In someembodiments, the charge holder 90 may be formed as a unitary body formedof a metal, plastic, composite, ceramic, and/or other suitable material.In some embodiments, the charge holder 90 may be formed of a materialthat disintegrates or is consumed upon use.

In embodiments, the body 93 of the charge holder 90 may be asubstantially solid cylinder. For the purposes of the presentdisclosure, a cylinder is considered “solid” if at least twenty fivepercent of a radius 101 from a center of the passage 94 to the outersurface 91 is formed of a solid material. Other suitable embodiments mayhave solid material forming at least forty percent, at least fiftypercent, or at least seventy five percent of the radius 101. A “solid”cylinder, as referred to in the present disclosure, is in contrast to a“hollow” cylinder. A hollow cylinder has a wall that makes up less thanforty percent of the radius 101. A conventional tube or pipe isrepresentative of a hollow cylinder.

FIG. 3B illustrates one non-limiting embodiment of a charge holder 96for the gun 60 (FIG. 1). The charge holder 96 is similar to that of thecharge holder 90 (FIG. 3A). However, the cavities 92 are arranged on twoplanes 74, 76 (FIG. 1). In this embodiment, the cavities 92 of eachplane 74, 76 are out of phase by forty-five degrees with one another.

FIG. 4 illustrates a carrier 100 that may be used with the perforatingguns 50, 60 (FIG. 1). The carrier 100 includes a bore 102 for receivinga charge holder, e.g., charge holder 90. Also, a circumferential groove94 is formed on the outer surface to provide a weakened wall sectionthat allows perforating jets to exit a perforating gun with less loss ofenergy. The groove 94 extends all the way around the carrier 100.Therefore, there is no need for angular/circumferential alignmentbetween the shaped charges 70 and the circumferential groove 94. Rather,the carrier 100 needs only an internal stop 97 to axially align theshaped charges 70 with the groove 94. By “axially aligned,” it is meantthat the shaped charges 70 and the circumferential groove 94 are at thesame plane 72 (FIG. 1) that is transverse to the long axis 11 (FIG. 1).

It should be noted that the charge holder 90 may be radially“free-floating” in the bore 102 of the carrier 100. By “free-floating,”it is meant that the charge holder 90 can move laterally, or transverseto the long axis 11 (FIG. 1). The charge holder 90 is only limited inthis lateral movement by the inner wall defining the bore 102. There areno structures connected to the charge holder 90 that restrict lateralmovement.

Referring to FIG. 3A, the arrangement of multiple shaped charges alongone plane may be advantageous during hydraulic fracturing operations.The shaped charges 70 (FIG. 1) form perforations 80 along the same plane72 (FIG. 1). Thus, hydraulic fracturing fluid 110 flows out of theperforations 80 at the same axial location, but at differentcircumferential locations. Directing fracturing fluid 110 in this mannermay minimize the tortuosity of the “fraccing” event and minimize thepressures required to create formation fractures and allow betterproppant placement.

From the above, it should be appreciated that perforating guns accordingto the present disclosure can be relatively short; e.g., less than onefoot. Further, the use of the charge holders 90, 96 may eliminate theneed for end plates or other similar structures used to support aconventional charge holding structure.

The above perforating tools may be used to complete a hydrocarbonproducing well. Referring to FIG. 5, there is shown a well constructionand/or hydrocarbon recovery facility 101 positioned over a subterraneanformation of interest 102. The formation 103 is an unconventionalformation. As described above, the nature of the unconventionalformation 103 is that the rock and earth, which is usually a type ofshale, is highly non-permeable; i.e., a permeability that is less thanten millidarcy (mD).

The facility 101 can include known equipment and structures such as arig 106 and a production structure 108. The production structure 108 caninclude casing, liners, cement, and other wellbore equipment. A workstring 110 is suspended within a wellbore 10 from the rig 106. The workstring 110 can include drill pipe, coiled tubing, wire line, slick line,or any other known conveyance means. The work string 110 can includetelemetry lines or other signal/power transmission mediums thatestablish one-way or two-way telemetric communication. A telemetrysystem may have a surface controller (e.g., a power source) 112 adaptedto transmit electrical signals via a suitable cable or signaltransmission line.

A perforating gun train 140 is shown in a deviated section 142 of thewellbore 10. The gun train 140 may include one or more guns according tothe present disclosure, e.g., guns 50, 60. By deviated, it is meant asection of the wellbore 10 is not vertical. The deviation from avertical datum can be between one to ninety degrees (horizontal) orgreater in some instances. In embodiments, the deviation may be greaterthan thirty degree, greater than forty five degree, or greater thansixty degrees. By way of reference, a deviation less than ninety degreeswould have the section 142 pointed downward and a deviation greater thanninety degrees would have the section 142 pointed upward. By “pointed,”it is meant the direction along which the wellbore 10 was drilled.

When fired, the perforating gun train 140 creates one or more openingsas shown in FIGS. 2A and/or 2B.

It should be understood that the teachings of the present disclosure aresusceptible to numerous variants and embodiments. Non-limiting variantsare described below.

As noted above, the present disclosure is not limited to any particularnumber of shaped charges per plane. A plane may include only one shapedcharge, two shaped charges, three shaped charges, or four or more shapedcharges. Also as discussed above, while not required, shaped charges maybe evenly distributed along their respective planes; e.g., 180 degreesapart for two shaped charges, 120 degrees apart for three shapedcharges, 90 degrees apart for four shaped charges, etc.

Referring to FIG. 6, in certain embodiments, a carrier 100 may includeone or more scallops 160 to reduce a wall thickness. The scallop 160 iscontrasted from the circumferential groove 94 (FIG. 4) in that thescallop 160 is a localized reduction in wall thickness of the carrier100. The shaped charge(s) 70 may be aligned with the scallop(s) 160using a key 162 fixed to the charge holder 90 that seats within a grooveor keyway 164 formed along an inner surface of the carrier 100. Thus,when the key 162 seats within the keyway 164, there is circumferentialalignment between the shaped charge(s) 70 and the scallop(s) 160. Whenthe charge holder 90 abuts the internal stop 97, the scallop(s) 160 areaxially aligned with the shaped charges 70. It should be understood thatthe key 162 and keyway 164 are merely illustrative of the alignmentmembers that may be used to circumferentially align the shaped charge(s)70 with the scallops(s) 160. Other alignment members may use snaprings/slots, pins/bores, etc.

Referring to FIGS. 7A-C, there are shown different arrangements fordetonating shaped charges 70. In these arrangements, it should beappreciated at a single detonating device detonates all of the shapedcharges 70 in a common plane. Further, in these arrangements, all of theshaped charges 70 are directly energetically coupled to a detonatingdevice. By “directly energetically coupled,” it is meant that thedetonation energy from a detonating device is transmitted to the shapedcharges 70. The shaped charges 70 may or may not be in physical contactwith the detonating device, but are sufficiently close enough that theenergy released by the detonating device detonates the shaped charges70. Thus, in a direct energetic coupling, no intervening energeticelement external to the shaped charge is used transfer a detonation froma detonating device to the shaped charges.

In FIG. 7A, the shaped charges 70 are detonated directly by a detonatingcord 170. The detonating cord 170 may be detonated by a detonator 172,that is directly or indirectly activated by a signal sent from thesurface. In FIG. 7B, the shaped charges 70 include booster charges 176,which are detonated by the detonating cord 170. The booster charge 176may be internal to the shaped charge 70 and not a separate element. InFIG. 7C, the shaped charges 70 are detonated directly by the detonator172, which may be directly or indirectly activated by a remote signal.Optionally, the shaped charges 70 may include internal booster charges176. Thus, it should be appreciated that a detonating device is anydevice that releases sufficient energy (e.g., thermal energy, shockwaves, pressure wave, etc.) capable of detonating a plurality of shapedcharges 70, all of which are on a common plane via a direct energeticcoupling.

FIGS. 8A and B illustrate embodiments of a charge holder 90 that issegmented segments. Referring to FIG. 8A, the charge holder 90 may be acylindrical body that includes three body segments 190. In onearrangement, each body segment 190 is “pie shaped;” i.e., generallydefined by two radii from a center and an arc. The surfaces aligned witheach radii may be considered radial surfaces. The radial surfaces ofeach body segment 190 are contiguous with one another such that, whenassembled, the body segments 190 form a solid cylindrical body. Eachbody segment 190 has a cavity 192, which may be a pocket, formed on anouter surface 194 of the body segment 190. Each cavity 192 may bedefined by an interior seating surface 196 against which the shapedcharge 70 (FIG. 1) seats, which may be the same as the seating surface95 (FIG. 3A) described previously. The segmented charge holder 90includes a central passage 200 for receiving the device that detonatesthe shaped charges 70 (FIG. 1), e.g., detonating cord, booster charge,bi-directional booster charge, detonator, a device providing ahigh-order detonation, etc.

FIG. 8A shows a charge holder 90 with three body segments 190 whereasFIG. 8B depicts an arrangement that has four body segments 202. The bodysegments 190, 202 may be molded of a non-metal, such as plastic. Thebody segments 190, 202 may be held together in a cylinder by anysuitable means. For example, an O-ring may be fitted into one or moregrooves 205 formed on the body segments, e.g., body segment 202.Additionally or alternatively, other retaining members, such as clips,fasteners, adhesives, etc. may be used to secure the body segments 190,202 to one another.

Additionally, in some embodiments, the body segments 190, 202 may be acasing of a shaped charge; i.e., an energetic material (not shown) maybe disposed in the cavity 192, which is then enclosed by a suitableliner (not shown). It should be appreciated in such embodiments, aperforating tool eliminates a charge holder; i.e., the shaped chargesare self-supporting in a carrier. By “self-supporting,” it is meant thatthe shaped charges structurally can support one another to maintain adesired relative orientation.

It is emphasized that the perforating tools of the present disclosure isnot limited to any particular shaped charge design or configuration.Merely for better understanding, there is illustrated in FIG. 9, onesuitable shaped charge 70 that may be used with the above-describedperforating tools. The shaped charge 70 may have a frusto-conical chargecase 224. The charge case 224 is open at the outer end 230. Disposedwithin the interior of the case 224 is a liner 228 having a generallyconical or frusto-conical configuration. Disposed between the liner 228and interior wall 226 of the casing 224 is an explosive material 234.The charge case 224 has an apex 236 at a closed end 238. A detonatingdevice 240 for detonating the explosive 234 is positioned adjacent tothe apex 236. In this configuration, it should be noted that the apex236 does not enclose the detonating device 240. As seen in FIG. 10, theapex 236 is shaped to be sufficiently narrow to allow a plurality ofshaped charges 70 to be circumferentially arrayed on the same planearound the detonating device 240. Thus, in one aspect, the detonatingsurface may be defined by an outer surface. All of the shaped charges 70have an energetic coupling with this outer surface. While the outersurface may define a circumferential body, the outer surface may alsodefine other geometric shapes such as squares, rectangles, ovals,triangles, etc. Regardless of the geometric shape, there are multipleenergetic couplings to such an outer surface. While the apex 236 isshown as a concave surface, the apex 236 may also be flat or have anyother geometry.

It should be noted that for the FIGS. 8A, B embodiments, a shaped charge70 as configured in FIG. 9 may modified as previously described. Thatis, the body segment 190, 202 (FIGS. 8A,B) is the charge case 224 (FIG.9), in such case they may be referred to as charge case segments.Because the assembly of charge case segments 190, 202 form a cylindricalbody of shaped charges that can be directly inserted into a carrier 100(FIG. 4), a separate structure for holding the shaped charges, such as acharge tube or strip, is not required. That is, the shaped charges areconsidered self-supporting in the carrier 100 (FIG. 4).

A non-limiting embodiment of a perforating tool having self-supportingshaped charges may include a carrier, a shaped charge assembly disposedin the carrier, and a detonating device disposed in the carrier. Theshaped charge assembly may include a plurality of shaped charges. Eachshaped charge may include a charge case, an explosive material disposedin the charge case, and a liner enclosing the explosive material in thecharge case. The shaped charges may be circumferentially disposed aroundthe detonating device such that all of the shaped charges are on thesame plane, the plane being transverse to a long axis of the carrier.Additionally, each charge case has a radial surface substantiallycontiguous with a radial surface of an adjacent shaped charge. Thecharge cases are arranged to form a solid cylindrical body. Optionally,a retaining member may be disposed around the shaped charges to securethe shaped charges to one another. Optionally, the shaped charges mayhave a direct energetic coupling to the detonating device.

Referring to FIGS. 3A and 9, as described previously the seating surface95 may generally follow the curvature or angle of an outer surface 250of the charge case 224 of the shaped charge 70. The seating surface 95may be contiguous for some or all of the outer surface 250. For example,in some embodiments, the seating surface 95 may be contiguous with theseating surface 95 for at least twenty five percent of a linear distance252 between the base 230 and the apex 232. In other embodiments, thecontiguous distance between the base 230 and the apex 232 may be atleast forty percent, at least fifty percent, or at least seventy fivepercent. In other embodiments, the seating surface 95 is completelycontiguous and only disrupted by an opening (not shown) through which atleast the apex 236 is positioned in the passage 94 or passage 200 (FIG.8A). By “contiguous,” it is meant that the seating surface 95 generallyfollow the curvature of the outer surface 250. Continuous physicalcontact is not required. Similar percentages for contiguous distance maybe used for the interior seating surface 196 illustrated in FIG. 8A.

FIG. 11 illustrates the seating surface 95 associated with the pockets92, 192 described above. The seating surface 95, 196 terminates at anopening 193 through which the apex 236 (FIG. 9) enters the passage 94 orpassage 200 as described previously.

In the context of the present disclosure, a detonation is a supersoniccombustion reaction, which can create shock waves and release thermalenergy. High explosives (RDX, HMX, etc.) are materials that willdetonate. A detonator is a device used to trigger an explosive material,such as the explosive material in a shaped charge or a detonating cord.Detonators can be mechanically or electrically initiated.

The foregoing description is directed to particular embodiments of thepresent disclosure for the purpose of illustration and explanation. Itwill be apparent, however, to one skilled in the art that manymodifications and changes to the embodiment set forth above are possiblewithout departing from the scope of the disclosure. Thus, it is intendedthat the following claims be interpreted to embrace all suchmodifications and changes.

1. An apparatus for perforating a subterranean formation, comprising: acharge holder having a passage along a long axis; a detonating devicepositioned in the passage; and a plurality of shaped charges supportedby the charge holder and circumferentially distributed along a sameplane that is transverse to the long axis, wherein each shaped charge isformed of at least a charge case, an explosive material disposed in thecharge case, and a liner enclosing the explosive material in the chargecase, and wherein all of the shaped charges are directly energeticallycoupled to the detonating device.
 2. The apparatus of claim 1, whereinthe charge holder is solid.
 3. The apparatus of claim 1, wherein thecharge holder includes a plurality of circumferentially distributedpockets formed on an outer surface of the charge holder, and whereineach pocket receives one shaped charge of the plurality of shapedcharges.
 4. The apparatus of claim 3, wherein each pocket has a seatingsurface complementary to a body of the shaped charge received therein.5. The apparatus of claim 1, wherein at least fifty percent of a radiusfrom a center of the passage to the outer surface is formed of a solidmaterial.
 6. The apparatus of claim 1, wherein the charge holderincludes a plurality of body segments.
 7. The apparatus of claim 6,wherein a body segment of each segment is the charge case of each of theplurality of shaped charges.
 8. The apparatus of claim 1, wherein thedetonating device is a detonator responsive to a surface signal.
 9. Theapparatus of claim 1, wherein the detonating device is one of: (i) abooster charge, and (ii) a detonating cord.
 10. The apparatus of claim1, further comprising a carrier having a bore receiving the chargeholder, the carrier having a circumferential groove extending fullyaround an outer surface, the circumferential groove being axiallyaligned with the plurality of shaped charges.
 11. A method forcompleting an unconventional subterranean formation, comprising:positioning a perforating tool in a section of the wellbore thatintersects the unconventional formation, wherein the wellbore isdeviated from a vertical datum, the perforating tool including: a chargeholder having a passage along a long axis; a detonating devicepositioned in the passage; and a plurality of shaped charges supportedby the charge holder and circumferentially distributed along a sameplane that is transverse to the long axis, wherein each shaped charge isformed of at least a charge case, an explosive material disposed in thecharge case, and a liner enclosing the explosive material in the chargecase, and wherein all of the shaped charges are directly energeticallycoupled to the detonating device; and firing the perforating tool toform at least one opening in the unconventional formation.
 12. Themethod of claim 11, further comprising: fracturing the formation bypumping a fracturing fluid through the at least one opening.
 13. Themethod of claim 11, wherein the deviation is at least forty five degreesfrom the vertical datum.
 14. The method of claim 11, wherein theunconventional formation has a permeability that is less than tenmillidarcy (mD).